Man pleads guilty in Family Research Council shooting

2/6/13 11:53 PM EST

A Virginia man pled guilty Wednesday to shooting a security guard last August at the offices of the conservative Family Research Council in downtown Washington.

Floyd Lee Corkins, 28, of Herndon, admitted to three felony charges: committing an act of terrorism while armed, assault with intent to kill while armed and interstate transportation of a firearm and ammunition. A security guard was shot and wounded while trying to subdue the gunman.

Corkins admitted that he targeted the FRC because of its opposition to gay marriage, the Justice Department said in a press release.

"Were it not for the heroic guard who tackled Floyd Corkins, he could have succeeded in perpetrating a mass killing spree in the nation’s capital,” said U.S. Attorney Ronald Machen.

Machen also used the case to advance the argument for President Barack Obama's recent proposal to limit ammunition clips to 10 rounds. Two magazines and additional boxed ammunition was found in Corkins's backpack, according to court documents.

“This case highlights the dangers of access to high-capacity magazines that allow killers to inflict carnage on a mass scale in the blink of an eye. Today’s guilty plea makes clear that using violence to terrorize political opponents will not be tolerated," Machen said in a statement.

Corkins faces a potential maximum sentence of up to 70 years in prison. However, judges usually sentence defendants in accordance with sentencing guidelines that call for lesser sentences in most instances.